What is the management approach for a patient with influenza-induced myocarditis leading to cardiac arrest?

Management of Influenza-Induced Myocarditis with Cardiac Arrest

Patients with influenza-induced myocarditis who suffer cardiac arrest require immediate initiation of oseltamivir 75 mg orally twice daily for 5 days (regardless of symptom duration), combined with advanced cardiac life support, and early consideration of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for refractory cardiogenic shock, though mortality remains extremely high even with maximal support. 1, 2

Immediate Resuscitation Phase

Standard ACLS Protocol

• Follow standard cardiac arrest protocols with high-quality chest compressions and defibrillation as indicated 3
• Establish IV access and obtain immediate ECG to assess for ST-segment changes, Q waves, low-voltage QRS complexes with electrical alternans, or conduction abnormalities 1
• Obtain cardiac troponin I or T levels immediately, as these are far more sensitive and specific for myocardial injury than CK-MB alone 1

Airway Management Considerations

• If intubation is required, use full personal protective equipment given the aerosol-generating nature of the procedure and high viral infectivity of influenza 3
• Consider using a small resuscitation team to limit potential exposure 3

Antiviral Therapy - Critical First Step

Initiate oseltamivir immediately upon suspicion of influenza-related cardiac complications:

• Adult dosing: 75 mg orally twice daily for 5 days 1
• Adjust to 75 mg once daily if creatinine clearance is less than 30 mL/min 1
• Do not delay antiviral therapy based on symptom duration—cardiac involvement mandates immediate treatment 1
• If patient cannot take oral medications, consider nasogastric administration once airway is secured 3

Hemodynamic Support and Monitoring

Initial Stabilization

• Assess for volume depletion and provide intravenous fluids as clinically indicated 1, 4
• Provide oxygen therapy targeting PaO2 greater than 8 kPa and SaO2 ≥92% 1
• Monitor vital signs at least twice daily once stabilized 1, 4
• Attach continuous cardiac monitoring and evaluate blood pressure frequently 4

Mechanical Circulatory Support Decision-Making

Consider VA-ECMO for refractory cardiogenic shock with the following indications:

• Persistent hypotension despite vasopressor support 1
• Severe cardiac dysfunction on echocardiography with clinical decompensation 1
• Inability to maintain adequate end-organ perfusion 2

Critical caveat: While VA-ECMO can provide temporary cardiopulmonary support (mean duration 6-8.5 days), mortality remains 33-100% in published series, with influenza-related myocarditis having significantly worse outcomes than other causes of cardiogenic shock 5, 2. The 2020 study from the European Respiratory Journal showed 100% mortality in seven patients with influenza-related myocarditis despite combined VA-ECMO and Impella support, compared to better outcomes in AMI-related shock 5.

The decision to pursue ECMO should weigh:

• Patient age and pre-existing conditions 5, 2
• Duration of cardiac arrest prior to ECMO consideration 6
• Presence of multi-organ failure, which ECMO cannot compensate for 5
• Institutional ECMO capabilities and expertise 2

Essential Diagnostic Workup

Obtain immediately:

• Full blood count, urea, creatinine, and electrolytes 1
• Liver function tests 1
• Chest radiograph 1
• Arterial blood gases 1
• 12-lead ECG 1, 4
• Echocardiography to assess cardiac function and guide mechanical support decisions 1

ICU Transfer Criteria

Transfer to intensive care for:

• Cardiogenic shock or persistent hypotension 1
• Severe cardiac dysfunction on echocardiography with clinical decompensation 1
• CURB-65 score of 4 or 5 if concurrent pneumonia is present 1
• Any patient requiring mechanical circulatory support 2

Prognostic Considerations

Key prognostic factors indicating poor outcome:

• Out-of-hospital cardiac arrest requiring extracorporeal cardiopulmonary resuscitation 5
• Multi-organ involvement beyond cardiac dysfunction 5
• Prolonged duration of cardiac arrest (>250 minutes), though rare survivals with intact neurologic function have been reported with ECMO 6
• Influenza B virus may cause particularly rapid and fatal myocarditis in previously healthy individuals 7, 2

Important pitfall: Do not assume cardiac arrest in influenza season is purely respiratory—maintain high suspicion for myocarditis and obtain troponins and ECG even in patients presenting with primarily respiratory symptoms 8. Severe cardiac dysfunction can be the leading clinical symptom of influenza infection 8.

Special Population: Pediatric Patients

• Children with influenza-related myocarditis can develop sudden cardiac arrest with rapid progression to death within 24 hours 7
• Early cardiac support may be the only option to prevent fatal outcome 7
• Triage to HDU/PICU after severity assessment 3
• Maintain oxygen saturation above 92% using nasal cannulae, head box, or face mask 3